Male aggression in the presence of an estrous female.

The relationship between male rat aggressiveness and the presence of a female was studied. Twenty 100-day-old dominant male albino rats were individually exposed to an inaccessible female rat in a specially constructed apparatus. The males were then given free-forced trials to an empty compartment or a compartment housing a submissive male. The results indicate that following exposure to an estrous female, dominant males increased their percentage of choices to the submissive male. Moreover, the incidences of aggressions by the dominant animal toward the submissive animal increased sharply after prior exposure to the estrous female. These data suggest that one antecedent source of aggression among male rodents may be the presence of a sexually receptive female.     

Tactile roughness of grooved surfaces: A model and the effect of friction

Previous experimental data on the roughness of grooved aluminum tiles provide a data base against which to test theories of roughness perception. A model based on the static deformation of the skin touching the stimulus tile is developed, and 11 parameters of the deformation are individually compared with the experimental data. All parameters were tested first in an approximate way, and then the better parameters were recalculated in a more exact manner. Three parameters, the depth to which the finger penetrates the groove, the cross-sectional area of the finger within the groove, and the cross-sectional area of the deviation of the skin from its resting position, all predict the roughness well as a function of finger force and groove width. The last of the three predicts roughness best as a function of land width, and is tentatively preferred as “the stimulus for roughness.” All predictions from the static model indicate that variation of the coefficient of friction between skin and tile should have little or no effect. This counterintuitive prediction was confirmed by an experiment.